This invention relates to thermally protected dynamoelectric machines and more particularly to improved means for holding thermal protectors in intimate thermal contact with the machine winding.
Reference is made to U.S. Pat. Nos. 3,319,096; 3,875,439; and to copending application Ser. No. 895,680, filed Apr. 12, 1978 now U.S. Pat. No. 4,203,045 issued May 13, 1980, and assigned to the present assignee, for background and disclosure of alternative means for mounting a thermal protector in intimate thermal relation with the winding of a dynamoelectric machine such as a fractional horsepower motor. Despite the availability of techniques that have previously been disclosed, there remains a desirability of having a thermal protector clamp offering a combination of features including ability to withstand a lateral pulling force, as is required in a fifteen pound pull test on thermal protector of a motor characterized by having open or removable end bells in order to secure Underwriters Laboratory's listing, while at the same time permitting use of the same thermal protector clamp on motors that may have a variation in the bulk or volume of the winding with which the thermal protectors are associated. Additionally, it is of course highly desirable that any such clamp be both economical and reliable in use and that it may be inserted by a simple assembly operation not entailing any high degree of expensor operator skill.
Motors with thermal protector clamps in accordance with the present invention achieve these multiple objectives. The clamp comprises a unitary metallic spring member that has a first portion engaging the protective device and forcing, by spring biasing, the protective device against the winding end turns while a second portion is disposed between the motor frame and the stator core and is a substantially flat member with, however, a pair of pointed lances extending toward and in engagement with the stack of laminations of the core on the surface of the stack on each side of the cleat member employed for securing the laminations together while the other surface of the second portion bears against the machine frame.
The clamp can be formed from a flat member of spring steel bent to provide the referred to portions. The first portion for holding the protector is at an angle in relation to the second portion that is inserted between the core and the frame and between the two portions is a spring portion which provides the resiliency that permits applying the clamp to protectors on various motors with a fairly consistent pressure of the protector against the winding although the winding bulk may differ. Additionally, the assembly operation is made simple by the fact that it is merely necessary that the clamp be inserted in the location where a slot or recess exists in the core and the frame as is provided by the cleating feature which is common to many fractional horse power motors. The lances are simple distended points from the principal portion of the clamp that is so inserted and permit relatively easy entry but difficult or impossible disassembly of the clamp from the core and frame structure.
The spring steel clamp is essentially unbreakable and may be economically formed to its desired configuration without requiring a high degree of precision in its formation or in its assembly with the thermal protector to the core and frame. It is therefore believed that the invention provides a simple and economical arrangement for maintaining the thermal protector in its desired location on the winding.